Method of making multilayer mat of particulate material

ABSTRACT

A method of making a multilayer mat or board comprises splitting an initial supply of particulate material into two parts and supplying one of such parts to a first forming machine and the other of such parts to a second forming machine positioned downstream of the first forming machine. The first forming machine spreads a first amount of the material on a moving conveyor at a rate in excess of that necessary to form a first layer on the conveyor. The second forming machine spreads a second amount of the material downstream of the first forming machine at a rate in excess of that necessary to form a second layer above the first layer. The excess material spread by the forming machines is removed by first and second scalpers positioned downstream of and adjacent each of said forming machines to insure uniform thickness of the layers. The invention is characterized by the fact that the excess material removed by the first scalper is returned to the supply for the second forming machine, and the excess material removed by the second scalper is returned to the supply for the first forming machine. In this manner the total supply of material to each of the forming machines remains substantially constant notwithstanding variations in the amounts of particulate material supplied to or fed from each of the machines.

United States Patent [72] Inventor Bohuslav E. Mikulka Richmond, Va.

[21] Appl. No. 31,531

[22] Filed Apr. 24, 1970 [45] Patented Jan. 4, 1972 [73] Assignee EvansProducts Company Portland, Oreg.

[54] METHOD OF MAKING MULTILAYER MAT OF PARTICULATE MATERIAL 3 Claims, 1Drawing Fig.

[52] US. Cl 117/19, 117/29,118/4l1,264/37, 264/113 [51] Int. Cl 1344c1/08, B44d 1/094 [50] Field ofSeareh 117/19, 29; 118/314,411,412;264/37,113

[56] References Cited UNlTED STATES PATENTS Assistant ExaminerJ. R.Batten, Jr. Attorney-Buckhom, Blore, Klarquist and Sparkman ABSTRACT: Amethod of making a multilayer mat or board comprises splitting aninitial supply of particulate material into two parts and supplying oneof such parts to a first forming machine and the other of such parts toa second forming machine positioned downstream of the first formingmachine. The first forming machine spreads a first amount of thematerial on a moving conveyor at a rate in excess of that necessary toform a first layer on the conveyor. The second forming machine spreads asecond amount of the material downstream of the first forming machine ata rate in excess of that necessary to form a second layer above thefirst layer. The excess material spread by the forming machines isremoved by first and second scalpers positioned downstream of andadjacent each of said forming machines to insure uniform 1,201,18710/1916 Jaek 117/19 thickness of the layers. The invention ischaracterized by the 1, ,056 1/ 1926 \ll/elch... 117/ 19 X fact that theexcess material removed by the first scalper is ,200 10/1933 Lipsius.117/19 UX returned to the supply for the second forming machine, and 2,1,2 3/ 1940 Avery 1 17/ 19 the excess material removed by the secondscalper is returned 2,268,890 1/ 1942 Mortensen, Jr. 1 17/19 UX to thesupply for the first forming machine. In this manner the 2,349,1535/1944 Ferrante 117/29 total supply of material to each of the formingmachines 2,743,758 5/1956 Uschmann 264/113 X remains substantiallyconstant notwithstanding variations in 2,900,270 8/1959 Klein 118/314Xthe amounts of particulate material supplied to or fed from 3,435,1063/1969 Hager 264/1 13 each of the machines.

26 1 SPLITTER FORMING MACHINE figgg TOP LAYER 53231:?

T CORE LAYER 4O FORMING SCALFER CORE LAYER MACHINE 1 34 BOTTOM a? L l9SUL'PERX View) 3a LAYER a 1 on, K I 20 30 b \QX |8SCALPER we/Wa n :gi//w/m 296% f flame/ alesz'gsvl PAIENIEDM 4m IN VEN TOR ATTORNEYS METHODOF MAKING MULTILAYER MAT OF PARTICULATE MATERIAL BACKGROUND OF THEINVENTION This invention relates to the manufacture of multilayer matsor boards, and more particularly, to the manufacture of such mats orboards having a core section comprising one or more layers disposedbetween top and bottom layers of identical thickness and weight.

Multilayer mats or boards are generally manufactured in a continuousprocess wherein the boards are formed on a continuously moving conveyorby laying down a face layer of particulate material, thence the corematerial and finally, the opposite face layer. It is desirable to havethe two face layers be of identical weight and thickness so as tominimize warping The material for such face layers is usually fed toseparate forming machines from a common source through a splitter in thefeed system. It is important to have identical feed rates to themachines depositing the opposite face layers and this has required thatthe particulate material be evenly split in the feeding apparatus.Obtaining such an even split has been a serious problem heretofore. Thisinvention is intended to overcome this problem.

It is thus the primary object of the present invention to provide amethod of making multilayer structures of particulate material havingtop and bottom layers of identical weight and thickness.

It is a further object of the present invention to provide a method ofmaking such structures wherein the supply of material to the formingmachines which deposit the top and bottom layers is maintainedsubstantially constant.

It is a still further object of the present invention to provide such amethod wherein substantially constant supplies of particulate materialare provided to the forming machines for the top and bottom layersnotwithstanding unequal adjustment of the splitting means in the initialfeeding system.

It is a still further object of the present invention to provide amethod such that volumetric control of the supply of material to theforming machines remains substantially perfect even over extendedperiods of time.

SUMMARY OF THE INVENTION In the manufacture of multilayer mats or boardsfrom deposited particulate material, or mats or boards having amultilayer core, especially with outside layers of a different materialthan the core layers, an initial supply of material for the outsidelayers is initially divided into two parts in the feed system. One ofsuch parts is supplied to a first depositing means and the other of suchparts is supplied to a second depositing means positioned downstream ofthe first means. Such first depositing means deposits a first amount ofthe particulate material on a moving means at a rate in excess of thatnecessary to form a first layer on the moving means. The seconddepositing means deposits a second amount of the material downstream ofthe first depositing means at a rate in excess of that necessary to forma second layer of such material above the first layer. The excessmaterial deposited by the first and second depositing means is thenremoved by first and second removing means positioned downstream of andadjacent the first and second depositing means, respectively.

The invention contemplates that the excess material removed by the firstremoving means be returned to the supply for the second depositingmeans, and the excess material removed by the second removing means bereturned to the supply for the first depositing means. In this manner,the total supply of particulate matter to each of the depositing meansremains substantially constant, notwithstanding variations in theamounts of particulate material supplied to each of such depositingmeans caused by unequal division of the initial supply thereto.

Llt

BRIEF DESCRIPTION OF THE DRAWING The FIGURE is a schematic illustrationshowing the general arrangement of a forming line in the process offorming a multilayer mat from particulate material on a moving conveyor.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing aforming line for forming a multilayer cellulose mat or board 8 isillustrated in a typical arrangement. A conveyor 10 moves to the leftunderneath a series of four forming machines l2, 13, I4 and 15 whichdeposit the particulate material I6 required to form the top, bottom andcore layers I7, 18, H9 and 20, respectively.

In accordance with the preferred practice it is highly desirable thatthe top layer I7 and the bottom layer 18 be of identical weight andthickness so as to minimize warping of the ultimate product. Thus thematerial for layers 17 and I8 is fed to the respective forming machines12 and 13 through a splitter 22 in the feed system.

The splitter 22 divides the material initially into two parts. One ofsuch parts is fed through a line 24 into the bottom layer formingmachine 13 which deposits the same directly onto the belt 10. The otherof such parts is fed through a line 26 to the top layer forming machine12 which is positioned downstream of the machine 13. Other particulatematerials are fed to the core layer forming machines 14 and 15 for thedepositing of the intermediate or core layers 19 and 20, respectively.These core layer forming machines do not otherwise enter into theinvention.

In the formation of mats and boards from particulate material, it iscustomary for each forming machine to deposit the material at a rate inexcess of that necessary to form the respective layer. The excessmaterial is then removed by a shaveoff or scalper positioned downstreamof and adjacent each forming machine to insure an accurate and uniformthickness of the respective layer. Thus, the material deposited for thebottom layer 18 by the forming machine 13 is removed or shaved off by ascalper 30 positioned downstream of and immediately adjacent the machine13. Similarly, a scalper 32 removes the excess material deposited by thetop layer forming machine 12. Additional scalpers 34 and 36 remove theexcess core layer materials deposited by the forming machines 14 and 15,respectively.

In accordance with the invention, the excess material removed by thescalper 30 is removed through a vacuum hood 38 and returned through aline 40 to the supply for the top layer forming machine 12. Similarly,the excess material shaved off by the top layer scalper 32 is removedthrough a vacuum hood 42 and returned through a line 44 to the supplyfor the bottom layer forming machine 13.

Such crossover feedback of excess material removed by the respectivescalpers for the top and bottom layers results in the total supply ofparticulate material for each of the forming machines 12 and I3remaining substantially constant notwithstanding variations in theamounts of materials initially supplied to each of such machines causedby unequal splitting by the splitter 22 or by variations in the depositrate. This will be readily seen by considering the following analysis.

If we let a represent the total flow of material necessary for theformation of the top and bottom layers 17 and 18, respectively, suchdesirably should be divided by the splitter 22 into two precisely equalflows a/2. Since the function of the scalpers 30 and 32 is to insure anaccurate and uniform thickness of the deposited layers by shaving themoff to the desired height, it is customary to deposit an excess amountof material, and this excess can be represented by c which generallyvaries between 10 and 30 percent of the required flows a/2.

If the division of the initial flows by the splitter 22 were perfeet,the material removed by the vacuum hoods 38 and 42 would each be equalto the constant value c. Since however, no splitting device can functionwith percent accuracy, the resulting flow rates through lines 24 and 26are not precisely equal and they may be represented as Flow to bottomlayer Flow to top layer where b is the deviation between thetheoretically equally split flows (1/2 and that which actually passesthrough each of the lines 24 and 26.

Since the flow through line 26 to the top layer forming machine 12 is(a/2b), the amount removed by scalper 32 and recirculated through line44 to the bottom layer forming machine 13 is Material removed by toplayer scalper 32 =c-b Thus,

Total feed rate into bottom layer forming machine [3 =Feed rate fromsplitter recirculation from scalper 32 Total feed rate into formingmachine 13 =(fl/ Total feed rate into forming machine 13 =a/2+cSimilarly,

Total feed rate into =(a/2-I7H-(c-l-b) Total feed rate into WA t nforming machine 12 =a/2-t-c Removed by each scalper c Rate of depositinto each of top and bottom layers lt is thus seen that the total supplyof particulate material to each of the top and bottom layer formingmachines 12 and 13 remains substantially constant notwithstandingvariations in the amounts of material initially supplied to each causedby unequal splitting in the initial supply. Even with a relatively largedifference in the two initial flows, as would be obtained with arelatively poor adjustment of the splitter 22, the volumetric control ofthe amount deposited remains perfect over extended periods of time.

Having illustrated and described certain preferred embodiments of theinvention, it should be apparent that the invention permits ofmodification in arrangement and detail. I claim all such arrangements ascome within the scope and purview of the appended claims.

I claim:

I. In a method of making a multilayer continuous structure fromdeposited particulate material comprising dividing an initial supply ofparticulate material into two parts;

supplying one of said parts to a first depositing means and the other ofsaid parts to a second depositing means positioned downstream of saidfirst depositing means;

said first depositing means depositing a first amount of said materialon a moving means at a rate in excess of that necessary to form a firstlayer on said moving means;

said second depositing means depositing a second amount of said materialdownstream of said first depositing means at a rate in excess of thatnecessary to form a second layer of said material above said firstlayer; and

removing the excess material deposited by said first and seconddepositing means by first and second removing means positioneddownstream of and adjacent said first and second depositing means,respectively;

the improvement comprising:

returning said excess material removed by said first removing means tothe supply for said second depositing means and said excess materialremoved by said second removing means to the supply for said firstdepositing means,

wherein the total supply of particulate material to each of saiddepositing means remains substantially constant, notwithstandingvariations in the amounts of particulate material supplied to each ofsaid depositing means material comprising splitting an initial supply ofparticulate material into two pans; supplying one of said parts to afirst forming machine and the other of said parts to a second formingmachine positioned downstream of said first forming machine; said firstforming machine spreading a first amount of said material on a movingconveyor at a rate in excess of that necessary to form a first layer onsaid conveyor; said second forming machine spreading a second amount ofsaid material downstream of said first forming machine at a rate inexcess of that necessary to form a second layer of material above saidfirst layer; and removing the excess material spread by said first andsecond forming machines by first and second scalping means positioneddownstream of and adjacent said first and second forming machines,respectively, to insure uniform thickness of said first and secondlayers; the improvement comprising:

returning said excess material removed by said first scalping means tothe supply for said second forming machine and said excess materialremoved by said second scalping means to the supply for said firstforming machine, wherein the total supply of material to each of saidforming machines remains substantially constant notwithstandingvariations in the amounts of material supplied to each of said formingmachines caused by unequal splitting of the initial supply thereto. 3.In a method of making a three-layer cellulose board having a core layerdisposed between top and bottom layers of identical weight andthickness, said method comprising splitting an initial supply ofcellulose material into two parts,

one for each of said top and bottom layers; supplying one of said partsto a first forming machine and the other of said parts to a secondforming machine positioned downstream of said first forming machine;said first forming machine spreading a first amount of said cellulosematerial on a moving conveyor at a rate in excess of that necessary toform said bottom layer of said board on said conveyor; said secondforming machine spreading a second amount of said cellulose materialdownstream of said first forming machine at a rate in excess of thatnecessary to form said top layer of said cellulose board; said corelayer being spread by at least one core layer forming machine positionedintermediate said first and second forming machines, said core layerbeing spread at a rate in excess of that necessary to form said corelayer; and removing the excess material spread by said first and secondforming machines and by said core layer forming machine by first andsecond scalping means positioned downstream of and adjacent said firstand second forming machines, respectively, to insure uniform thicknessof said first and second layers, and by core layer scalping meanspositioned downstream of and adjacent said core layer forming machine toinsure uniform thickness of said core layer; the improvement comprising:

returning said excess material removed by said first scalping means tothe supply for said second forming machine and said excess materialremoved by said second scalping means to the supply for said firstforming machine, wherein the total supply of cellulose material to eachof said first and second forming machines remains substantially constantnotwithstanding variations in the amounts of cellulose material suppliedto each of said first and second forming machines caused by unequalsplitting of the initial supply thereto.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION.

Patent N 3 Dated January -4 1972 Inventor9 BOHUSLAV E. MIKULKA It iscertified that error appears in the above-ientified patent and that saidLetters Patent are hereby corrected as shown below:

Column 3, at line 25, should read Q Similarly,-

Total feed rate into forming machine 12 (a/Z b) (c b) Signed and sealedthis 6th day of June 1972 0 (SEAL)- Attest:

EDWARD M.FLETCHER,LTR. ROBERT GOT'I'SCHALK Attesting OfficerCommissioner of Patents

2. In a method of making a multilayer mat of particulate material comprising splitting an initial supply of particulate material into two parts; supplying one of said parts to a first forming machine and the other of said parts to a second forming machine positioned downstream of said first forming machine; said first forming machine spreading a first amount of said material on a moving conveyor at a rate in excess of that necessary to form a first layer on said conveyor; said second forming machine spreading a second amount of said material downstream of said first forming machine at a rate in excess of that necessary to form a second layer of material above said first layer; and removing the excess material spread by said first and second forming machines by first and second scalping means positioned downstream of and adjacent said first and second forming machines, respectively, to insure uniform thickness of said first and second layers; the improvement comprising: returning said excess material removed by said first scalping means to the supply for said second forming machine and said excess material removed by said second scalping means to the supply for said first forming machine, wherein the total supply of material to each of said forming machines remains substantially constant notwithstanding variations in the amounts of material supplied to each of said forming machines caused by unequal splitting of the initial supply thereto.
 3. In a method of making a three-layer cellulose board having a core layer disposed between top and bottom layers of identical weight and thickness, said method comprising splitting an initial supply of cellulose material into two parts, one for each of said top and bottom layers; supplying one of said parts to a first forming machine and the other of said parts to a second forming machine positioned downstream of said first forming machine; said first forming machine spreading a first amount of said cellulose material on a moving conveyor at a rate in excess of that necessary to form said bottom layer of said board on said conveyor; said second forming machine spreading a second amount of said cellulose material downstream of said first forming machine at a rate in excess of that necessary to form said top layer of saId cellulose board; said core layer being spread by at least one core layer forming machine positioned intermediate said first and second forming machines, said core layer being spread at a rate in excess of that necessary to form said core layer; and removing the excess material spread by said first and second forming machines and by said core layer forming machine by first and second scalping means positioned downstream of and adjacent said first and second forming machines, respectively, to insure uniform thickness of said first and second layers, and by core layer scalping means positioned downstream of and adjacent said core layer forming machine to insure uniform thickness of said core layer; the improvement comprising: returning said excess material removed by said first scalping means to the supply for said second forming machine and said excess material removed by said second scalping means to the supply for said first forming machine, wherein the total supply of cellulose material to each of said first and second forming machines remains substantially constant notwithstanding variations in the amounts of cellulose material supplied to each of said first and second forming machines caused by unequal splitting of the initial supply thereto. 